Patent Literature 1 has been well-known as a conventional electric connection box. This electric connection box is constituted by housing a circuit board in a case. An electronic component such as a relay is mounted in this circuit board. Energizing the electronic component causes heat to be generated. According to the electric connection box disclosed in Patent literature 1, heat generated from the electronic component would be diffused out of the case from an opening provided in the case.
With the opening provided in the case, dust intrusion from this opening into the case might cause a short-circuit between the electronic components. The electric connection box disclosed in the Patent literature 1 intends to prevent the dust intrusion by providing a louver in the opening. However, the louver cannot completely prevent the dust intrusion.
Considering the foregoing, the circuit board may be sealed in the case, without providing an opening in the case. However, according to the above configuration, heat generated from the electronic components remains inside of the case, and might cause a local and large temperature rise inside of the case. If so, for example, the temperature in a soldered part between the electronic component and the circuit board rises above the soldering heat-resistant temperature, and might degrade the connection reliability between the electronic component and the circuit board.
[Patent literature 1]: Japanese Unexamined Patent Publication No. H08-130817
The present invention has been made on the basis of the above circumstances, with an object of providing an electric connection box which is constituted so as to suppress a local and large temperature rise therein.